The nutrients NH4+, NO3−, Ca2+, Mg2+ and K+ in leachates from immediately below the forest floor and from the mineral horizons at 10- and 30-cm depths were monitored with tension lysimeter plates held at 10 ± 1.0 kPa. Experimental plot treatments were thinning, fertilizing with nitrogenous fertilizers (448 kg N∙ha−1), and both. Concentrations (mg∙L−1) of these nutrients in the forest floor leachates increased immediately following nitrogen fertilization, but returned to near those of untreated levels about 5–10 mo later. Concentrations fluctuated at 10- and 30-cm depths in the mineral horizons. With urea fertilization, the increases in concentrations of nutrients were primarily associated with the forest floor. Nitrate concentration of 200 mg N∙L−1 in the forest floor leachate 5 mo after urea fertilization compared to 0.1–0.5 mg N∙L−1 of the untreated, indicated that nitrification had taken place. With ammonium nitrate fertilization, substantially higher concentrations of NO3−, Ca2+, Mg2+, and K+ were detected at 10- and 30-cm depths compared with urea fertilization. Thinning, when combined with urea fertilization, enhanced the movement of nutrients to greater depth in the soil profile. On a unit area basis (kg∙ha−1) the leaching of nutrients from soil horizons could be overestimated by the tension lysimeter plate method, as these plates do not only draw soil water from directly above.
Dynamic of nitrogen and dissolved organic carbon in an alpine forested catchment: atmospheric deposition and soil solution trends